|Eggs||4 , separated|
|Pastry flour||1 3⁄4 Cup (28 tbs) (About 425 Milliliter)|
|Cornstarch||1⁄4 Cup (4 tbs) (About 50 Milliliter)|
|Baking powder||2 1⁄2 Teaspoon (About 12 Milliliter)|
|Salt||1⁄2 Teaspoon (About 2 Milliliter)|
|Fruit sugar||1⁄2 Cup (8 tbs) (About 125 Milliliter)|
|Soft butter||1⁄2 Cup (8 tbs) (About 125 Milliliter)|
|Milk||1 Cup (16 tbs) (About 250 Milliliter)|
|Vanilla||1 1⁄2 Teaspoon (About 7 Milliliter)|
Grease a 9 x 13 inch (3.5 L) pan and line with waxed paper.
Beat egg whites until foamy, then beat in fruit sugar gradually and continue beating until very stiff.
Sift next 5 ingredients into a bowl and drop in butter and egg yolks.
Measure in milk and vanilla.
Beat until smooth, scraping the sides of the bowl occasionally.
Transfer egg whites to a large bowl and fold in the flour mixture with a whisk.
Spread in pan.
Bake at 350F (180C) for 40 to 45 minutes.
Cool in pan 10 minutes, remove and cool completely.
Cover with a damp towel until Maple Double Boiler Icing is made, then frost smoothly.